Cyanhydrin interchange



Patented ()et. 14, 1941 V l r 2,259,161

UNITED STATES PATENT oFrrc CYANHYDRIN INTEBCHANGE Frederick E. Kiing, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application June 4, 1940, I Serial No. 338,756

12 Claims. (Cl; 260-464) This invention relates to 'a process for the discoverythat a cyanhydrin A, will react with preparation of cyanhydrins and more particularly an aldehyde or ketone B, in the presence of an to a process for the conversion of one cyanhydrin alkaline catalyst to yield the cyanhydrin of the to another by means of a cyanhydrin interchange first aldehyde or ketone, C, and another aldehyde reaction. 6 or ketone, D. The equation for the reaction may Aldehyde-and ketone cyanhydrins have recently be represented as:

A n o 1) Aldehyde or aldehyde'or aldehyde or aldehyde or ketone cyanhydrin kctonc ketono ketone p cyanhydrin become of increased importance as intermediates This reaction is not confined to any particuin the synthesis of many industrial organic chemlar compounds but is applicable to the broad icals. For example, acrylic nitriles, which are class of aldehyde or ketone cyanhydrins. Thus widely used in polymerization, may be obtained 15 the original aldehyde or ketone employed, B,

in good yields by the pyrolysis of. theacetyl derivmay be a symmetrical or asymmetrical alkyl, aryl, atives of certain aldehyde or ketone'cyanhydrins. aralkyl or cyclic ketone such, for example,- as It is desirable; therefore, that a method be proacetone, methyl ethyl ketone, diethyl ketone, vided by which these cyanhydrins may be premethyl propyl ketone, methyl isobutyl ketonc.

pared in good yields at the lowest possible cost. ethyl propyl ketone, benzophenone, methyl benzyl Heretofore, the corresponding cyanhydrins ketone, methyl cyclohexyl ketone and the like, or have been prepared by the reaction of aldehydes it may'be an alkyl, aryl or aralkyl aldehyde such, or ketones with hydrocyanic acid in the presence for example, as acetaldehyde, propionaldehyde, f an organic as s as py din or of som butyraldehyde, benzaldehyd-e and the like or an other suitable alkaline catalyst such as an oxide, equivalent or homolog of any of these aldehydes yd carbonate or y d of an a i or or ketones. Likewise the original cyanhydrin, A,

I alkaline earth metal. When this reaction is permay be the cyanhydrin of any of the above deformed usin ydrous hydrocyani acid it is scribed aldehydes or ketones or of their equivatages. Another object is to provide a method of necessary that the temperature and concentral nt r homologs, tions of the reactants becontrolled Ve y C os y, Since this cyanhydrin interchange reaction as oth rwise polymerizetions d/ r decompositions defined above is reversible,- an equilibrium is esoccur and th oyenhydrin s obtained in tablished between the concentrations of the Satisfactory yields and in a state of insufficient products and the reactants. The equilibrium P y. On the other hand, if q s hydroconstant for the reaction may be expressed in cyanic acid, which may be prepared by the action o terms of concentrations of an inorganic acid-on a metal cyanide in aque- (C) (D) ous solution, is reacted with a low molecular K= (71m) aldehyde such as acetaldehyde, it is diflicult to D separate the cyanhydrin from the aqueous salt In Vi w f h s oq lh rium tis desirable in the solution. 40 practice of this invention that oneof two condi- This invention has as one of 'its objects to tions be fulfilled in order -to-0btain good yields provide a new method of preparing cyanhydrins 0f the desired products.

not subject to the above mentioned disadvan- These conditions are: g

(1) The reactants should be chosen so that,

producing aldehyde or ketone cyanhydrins in at equilibrium, the COnCEXltI'fltlOIlS of the re good yields without the necessity' of preparing actants are very small in comparison to the con anhydrous hydrogen cyanide. Still another obcentrations of the products, i. e. K for the reacject is to provide a convenient method for the tion should be large.

preparation of cyanhydrins of aldehydes or ke- (2) Means should be provided: whereby the tones of low molecular weight which can not be equilibrium is continuously displaced toward the separated easily from aqueous solution. The at-'- right-as the reaction proceeds.

tainment of these and other objects will be ap- In carrying out the reaction according to conparent from the following description of this indition (1) above it will be necessary to select an vention. original aldehyde or ketone cyanhydrin, A. which The essence of this invention resides in the has a larger'dissociation constant than the aldehyde or ketone cyanhydrin which is formed, D.

The dissociation constants of aldehyde and ketone cyanhydrins stand in general in the following order, the compounds at the top of the list having the largest constants: v 5 self is also extracted from the water phase and a substantially all the hydrogen cyanide is found g ketone cyanhydrms. in the non-aqueous phase together with the cyanalkyl ketone cyanhydrms h drin For exam 1e if a solution of h dr en Cyclic ketone cyanhydrins y p y 0g Alk lketone cyanhydrins cyanide, or a solution containing metallic cyanide A {amen d c anh arms and an inorganic acid, be treated with methyl. A211 1 5 5 3; cygnhydrms' ethyl ketone, in excess over that required to form Alk m h d c anh d-rins the cyanhydrin, two layers are formed and over Y a Y 6 Y y 90% of the hydrogen cyanide will be found in the When a cyanhydrin is reacted with an aldeketone phase present eitherasketone cyanhydrin y 1 ketone Whose y hydrin is lower in the or. as dissolved hydrogen cyanide. Further exabove list than the original cyanhydrin, the retractions with ketone will remove practically all action proceeds substantially to completion since of the hydrogen cyanide from the water phase. 815 equilibriumrK Will be large. In many cases The ketone layer prepared in this way is then compound B in the general reaction will be an used as the ketone cyanhydrin, A, in a preferred aldehyde while compound D will be a ketone. embodiment of this invention. For example, Typical examples of the practice of this invention acetaldehyde. may be reacted with the methyl according to condition (1) are, accordingly, as ethyl ketone layer containing methyl ethyl ketone follows: .c'yanhydrin, and possibly hydrogen cyanide, as

.A B O n asser mam see Methylcthyl acetaldehyde acetaldehyde methyl ketone cyanhydrin cyanhydrin ethyl ketone Acetone formaldehyde formaldehyde acetone cyanhydrin 7 cyanhydrin Bcnzaldhyde butyraldchyde -v butyralde hyde benzaldehyde cyanhydrin I cyanhydrin When the reaction is performed 'in accordance with condition (1) the productsof the reaction may be separated from each other and from the reactants by any suitable means such is distillation, extraction, crystallization or the like. The reactants may be mixed in molar proportions or an excess of one of the reactants may been'rployed. A common solvent may also be employed if desired. Other conditions for the reaction will depend uponthe particular compounds used.

Another method of causing the-reactionto go to completion is to carry out the reaction in accordance with condition (2), that is, to displace the equilibrium continuously toward the right. This may be done in instanceslwhere one of the products may be separated from the reaction medium continuously as formed. The most convenient means'of accomplishing; this result is to distill off a lowboiling product of the reaction.

For example, if 'acetone cyanhydrin is reacted with methyl propyl ketonein the presence .of'an alkaline catalyst and the acetone which is formed by the cyanhydrin interchange is continuously removed by fractional distillation, methyl propyl I ketone cyanhydrin is obtained in good yields.

The substance used as'the catalyst for the general reaction of this invention may be any alkaline catalyst such as a hydroxide, oxide, caracetylated and then pyrolzed to this'compound. I

bonate or cyanide of an alkali or alkaline earth metal or an organic alkaline compound such as pyridine. Only small amounts of the catalyst are necessary.

In the practice of this invention the initial aldehyde or ketone cyanhydrin, A, may be prepared by any of the known means for preparing such compounds. The preferred method is to prepare thecyanhydrin, A, by the reaction of aqueous hydrogen cyanide (or a cyanide plus an inorganic acidin aqueous solution). with the aldehyde or ketone. In this method use is made of a'ketone o'r aldehyde which is immiscible with the aqueous hydrocyanic acid solution or whose cyanhydrin acted aldehyde or ketone. Hydrogen cyanide itprepared above to yield acetaldehyde cyanhydrin (lactonitrile) and methyl ethyl ketone. These may be separated; by distillation and the recovered methyl ethyl ketone may be reused. Other ketones such as methyl propyl ketone, methyl isobutyl ketone and dipropyl ketone have also been used in this process with good results. The overall yield of acetaldehyde cyanhydrin by this method is high, usually over and frequently as highas I This method is particularly adapted to the preparation of low molecular. aldehyde cyanhydrins such as formaldehyde cyanhydrin and acetaldehyde cyanhydrin since thesecompounds are obtamed-only with difficulty and in unsatisfactory,

yields by other methodsp since acetaldehyde cyanhydrin (lactonitrile) may be conveniently prepared by this reaction, this invention provides a convenient route to the preparation of acrylontrile since acetaldehyde cyanhydrin may be The particular conditions to be. used in the practice of this invention may be illustrated by the following preferred embodiments of the invention. It is to be understood however, that these examples are not intended in any way to limit the invention to the specific compounds or conditions described therein. a

Example 1 .Fifty' parts (1 mole) of 95% sodium' cyanide in parts of water and 100 parts 1.4 moles) of methyl ethyl ketone are treated with 54 parts (.55 mole) of 96% sulfuric acid in 100 parts of water. The temperature is kept at 45 C. during the addition of the acid. The mixture isstirred 10 minutes while the temperature fallsto 40 C. Two layers are formed which are separated. The upper non-aqueous layer is mixed with 0.5 part of sodium cyanide and then 45 parts (1.05 moles) of acetaldehyde are added. The mixture is stirred for one-half hour after which 1 part of 95% sulfuric acid is added and the mixture is distilled. A 90% yield of acetalde- .with a compound of hyde cyanhydrin based on the sodium cyanide is obtained.

Example 2.-,Jifty parts of pure acetaldehyde are run into 104 parts of methyl ethyl ketone cyanhydrin containing 0.5 part of sodium carbonate as catalyst,and the mixture" is stirred at 40 C. for one hour. parts of 75%,phosphoric acid are then added to prevent decomposition of the cyanhydrin and the mixture is distilled. An 88% yield of acetaldehyde cyanhydrin is obtained. (63 parts B.P. 20 min. 90-96 C.)

Example 3.Fifty four parts (.55 mole) of 96% sulfuric acid in 100 parts of water are added hydrin of said compound and hydrogen cyanide, reacting said layer with a compound of the class consisting of aldehydes and ketones, in the presence of an alkaline catalyst and driving the reaction to completion by continuously removing one of the products of the reaction.

5. The" method of preparing a cyanhydrin having both the'cyano and "the hydroxyl groups on the same carbon atom which comprises treating an aqueous solution of cyanide with an inorganic acid and a compound 01 the class consisting of aldehydes andfketones whose cyanto a mixture of 50 parts (1 mole) of 95% sodium cyanide, 100 parts of water and 100 parts (1.4 moles) of methyl ethyl ketone at a temperature maintained between 40 and 45 C. The mixture is stirred for 10 minutes.

Upon subsequent standing two liquid layers form which are separated. The upper non-aqueous layer is then mixed with 85 parts (1.05 moles) of 36% formalin." Solid sodium cyanide (.5 part) 'is added and the mixture is stirred for one hour at 30-35/C. A single liquid phase is present. 3

\ parts oi'flphthalic anhydride are added and the mixture is distilled at reduced pressure. Fortyhydrins may be salted out of aqueous solutions,

separating the non-aqueous layer containing the cyanhydrin of said compound and hydrogen cyanide, treating said layerwitha compound of the class consisting of aldehydes and ketones whose cyanhydrins have a smaller dissociation constant than the cyanhydrin of the first named compound, in the presence of an alkaline catalyst and'thereafter separating the products of the reaction.

6. The method of preparing an aldehyde cyanhydrin from a ketone cyanhydrin which comsix parts of formaldehyde cyanhydrin (B.

. P. in mm. 101-103 C.) corresponding to an 83% yield .are obtained. In this example phthalic anhydrlde is added to prevent decomposition of the cyanhydrin during distillation since a stronger acid leads to polymerization and tar forma-' tion.

Iclaim: f 1. The process which comprises reacting a cyanhydrin having both the cyano and thehydroxyl groups on the same carbon atom with a compound of the class consisting of aldehydes and ketones in the presence of an alkaline catalyst to form another similar cyanhydrin and another compound 0! the class consisting of aldehydes and ketones.

2. The process which comprises reacting a cyanhydrin having both the cyano and the hydroxyl groups on the same carbon atom with a compound of the class consisting of alde- .hydes and ketones in the presence of an alkaline catalyst to form another similar cyanhydrin and another compound of the class consisting of aldehydes and ketones, and continuously remov ing one of the products of the reaction.

\ 3. The method of preparing a cyanhydrin having both the cyano and the hydroxyl groups hydrin having a greater dissociation constant which comprises treating thepsecond cyanhydrin hydes and ketones in the presence of an alkaline catalyst and thereafter separating the products of the reaction.

4. The method of preparing a cyanhydrin having boththe cyano and the hydroxyl groups on the same carbon-atom which comprises axtracting an aqueous solution of hydrocyanic acid with a compound-of the class consisting of water insoluble aldehydes and ketones, separa-t--- prises treating said ketone cyanhydrin with an aldehyde in the presence of an alkaline catalyst and thereafter separating the ketone and the aldehyde cyanhydrin thus formed.

7. The method, of preparing a cyanhydrin of a low molecular alkyl aldehyde which comprises treating a ketone cyanhydrin withsaid aldehyde in the presence of an alkaline catalyst and thereafter separating the cyanhydrin of said aldehyde and the ketone thus formed.

8. The method of A preparing acetaldehyde' cyanhydrin which comprises reacting another cyanhydrin having both the cyano and hydroxyl groups on the same carbon'atom with acetaland thereafter separating the acetaldehyde g on the same carbonatom from a similar cyanthe class :onsisting o1 aldeing the non-aqueous layer containing the cyandehyde, in the presence of analkaline catalyst.

9. The method of preparing acetaldehyde cyanl'wdrin which comprises reacting a ketone cyanhydrin with acetaldehyde in the presence of an alkaline catalyst.

10. The method of preparing acetaldehyde cyanhydrin which comprises reacting aqueous sulfuric acid, sodium cyanide and methyl ethyl ketone, separating the methylethyl ketone layer containing methyl ethyl ketone cyanhydrin and hydrogen cyanide, treating said layer with acetaldehyde in the presence 01 an alkaline catalyst cyanhydrin and the methyl ethyl ketone.

11. The method ;of preparing formaldehyde "cyanhydrin which comprises reacting a ketone FREDERICK E. mine. 

